The present invention refers to a catheter coupling with integrated strain relief for allowing a catheter to be coupled to a syringe or to another liquid transfer device.
In epidural anesthesia, a catheter is introduced into the epidural space of a patient through a steel cannula. Subsequently, the steel cannula is withdrawn beyond the proximal catheter end, whereas the catheter remains in its position. The proximal end of the catheter must not have any enlargements or connecting devices, since the withdrawal of the steel cannula would be hindered thereby. After removal of the steel cannula, the catheter must be provided with a catheter coupling, e.g. in the form of a Luer-Lock connector, for connection to liquid supplying device. The catheter consists of a flexible hose with a small diameter. The outer diameter is generally less than 1 mm. A catheter coupling connected to the catheter must not squeeze the catheter so that the catheter lumen stays open.
From EP 0 415 665 A1, a catheter coupling is known, wherein the catheter is passed through an annular elastomer plug clamped between two screwed elements. By tightening the screw elements, the plug is rotated radially and pressed against the catheter with force. To operate the catheter coupling, two hands are required, while having to hold the catheter at the same time. An appropriate tightening of the catheter coupling would thus require three hands. More-over, the tightening requires great strength. When the catheter coupling has a Luer-Lock connector having to be turned for disengagement, there is a risk that the catheter coupling is opened instead of the Luer-Lock connector so that the catheter slips out.
Another hose coupling is described in U.S. Pat. No. 5 423 766. Here, the catheter coupling includes a trumpet-shaped tube member, the catheter being slipped onto the narrower end thereof. Subsequently, the clamping is performed with two clamping members tensioned by means of a bayonet catch. Again, inadvertently turning the bayonet catch may cause disengagement.
A catheter coupling with two articulated jaws is known from U.S. Pat. No. 4 006 744. Here, one of the jaws is provided with a hose piece through which the catheter is passed. The other jaw is folded over the hose piece, clamping the same. The catheter is held only by the radially pressed hose piece. In this case, there is a risk of inadvertently pulling out the catheter.
It is an object of the present invention to provide a catheter coupling with strain relief that is simple to apply to the catheter and guarantees a great holding force, without constricting the catheter.
According to the present invention, the jaws extend in the longitudinal direction of the hose piece receiving the catheter end and they are connected at the one end of the hose piece by a joint whose axis extends transversely to the hose piece. At the opposite end the jaws may be locked in the closed state. Thus, the end portion of the catheter to be clamped is engaged by the jaws in the longitudinal direction, thereby guaranteeing a-particularly good and safe hold, since a long covered portion can be realized. Further, when closing the jaws, the clamping force progressively increases from one end to the other. In this manner, a safe clamping is achieved over a relatively long distance.
Preferably, the grooves in the jaws that form the channel, does not have a continuous groove bottom, but the groove bottom has rises and indentations, to cause a wavy path of the hose piece when the jaws are closed. This generates high frictional resistance.
The catheter coupling is very easy to handle. It is only necessary to press the jaws against each other to close the channel. Moreover, there is no risk of the catheter coupling being inadvertently opened by turning movements as they are necessary for disengagement from a counter plug connector.
Preferably, the channel has at least two bends with a straight section in between. Here, the hose is deformed only in the bends, but not in the straight portion. This way, it is made sure that, with the jaws open, the hose assumes a stretched straight state so that the catheter can easily be introduced into the hose.